These city-states [ie Los Angeles, the Northeast megalopolis] matter far more than most American states.

LA may have more economic output than Wyoming, but this doesn't mean the city "matters" more. Indeed, I would assume that residents of Wyoming or Rhode Island or Mississippi, in fact believe that they and their homes do matter, that their local political issues and the solutions they attempt do indeed matter. And precisely one of the major tenets underlying the US system of government is to avoid concentrating political power in economic centers, lest the republic only serve its better-off, better-connected citizens. To my understanding, this is what motivates many aspects of our Constitution: the cumbersome division of our government into federal and state spheres, the division of our Congress into state and district representations, the electoral college, the designation of smaller cities as state capitals, to name a few. The author seems not to understand these principles, and even to disdain them:

While the economic reality goes one way, the 50-state model means that
federal and state resources are concentrated in a state capital — often a
small, isolated city itself — and allocated with little sense of the
larger whole. ...[This keeps] back our largest cities.

That's kind of the idea--to avoid a country of hyper-developed, hyper-powerful cities surrounded by disenfranchised hinterlands. We are already doing a pretty poor job of avoiding this outcome--why would we actively try to encourage it?